PHOTO: Benjamin Levin/CNN

It’s always a letdown when those last few sips of coffee bring only lukewarm disappointment. Sure, you can zap it in the microwave so it’s piping hot once again, or just toss it for a fresh cup. But modern problems require modern solutions, which is where the Ember Mug 2 comes in ($99.95; amazon.com). This clever cup maintains the heat of your drink at up to 145 degrees Fahrenheit, ensuring you never have to taste that room-temp coffee again.

What is the Ember Mug 2?

PHOTO: Benjamin Levin/CNN

The Ember Mug 2 is a rechargeable stainless steel mug surrounded by a ceramic coating (tip: do not microwave it). It comes in three styles: 10 ounces in white, 10 ounces in black and 14 ounces in black. It keeps your drink toasty by creating a convection current in whatever liquid you fill it with. It will automatically detect when liquid’s inside and begin heating. Likewise, it’ll go to sleep after a time if it’s empty. And while it can heat up liquids from cooler temperatures, its main purpose is to maintain the heat of an already piping beverage. Unfortunately, it can’t keep things cool, which would have been double the fun. But then again, a nifty invention called ice has us covered on that front.

By default, the mug aims to keep liquids at 135 degrees Fahrenheit. However, with the Ember app, you can define any temperature between 120 and 145 degrees Fahrenheit. The app provides both your selected temperature and the current temperature of your drink. Don’t worry, metric mates, you can change the readings to celsius in the settings.

Right on the front, beneath the Ember 2 logo, is an LED that provides info on both the status of your drink and the battery remaining in the mug. For example, when it’s slowly pulsing, that means it’s bringing your beverage up to temperature. Once it’s solid, that means it’s hit the sweet spot. And if the light is red, it’s time to charge up.

More on the app

PHOTO: Benjamin Levin/CNN

The Ember app is rather simple, but an app that controls a mug doesn’t need too many bells and whistles. Before you use it, you’ll need to pair your mug with the app. To do so, tap “Pair new device” after opening the app for the first time. Then, hold the power button on the bottom of the mug until the LED flashes blue. It should pair up soon after that.

Once you’re in the app, it will say “Empty” to indicate there’s nothing in your mug. On the bottom is a slider — use this to select your preferred temperature (up to 145 degrees Fahrenheit). Finally, pour in a hot beverage. Where it said “Empty” before, the app will now display the actual temperature of your drink. From there, the mug will do its work.

If you press the gear on the top right, there are a handful of settings as well as a section displaying the Ember Mug 2’s battery level. Basically, there are three things you can do: change the temperature units, turn on notifications and customize the LED. Yes, you can customize the LED’s color (and brightness) so you don’t mix up your warm milk with your partner’s mug of nearly-scalding tea. Finally, on the bottom of this section is a button to update the firmware, if such an update is available.

Back at the temperature screen, there’s a hamburger menu on the top left. From there, you can do things like pair another mug via “My Devices” or see tutorials and troubleshooting by tapping “Using your Ember”.

Taking a sip

PHOTO: Benjamin Levin/CNN

We had a great time with the 10-ounce Ember Mug 2. First and foremost, it does what it sets out to do: maintaining the heat of your drink. We steeped some tea, poured it in the mug and set its temperature to 140 via the Ember app. And then, over the course of about 45 minutes, we enjoyed a beverage that was satisfying to the last sip. Despite knowing what to expect, it was surprising to find our drink was still hot by the end.

The app was a cinch to use — just drag the slider to your preferred temperature and fill up the mug. That being said, it would have been nice if, when first opening the app, some text appeared to show us around. Even without the app paired, the mug will default to 135 degrees.

When we were finished up, it was easy to hand wash and dry. Ember advises you don’t dishwash the mug, though, which would have been a convenient feature to include. And for goodness’ sake, do not microwave this mug! Among other circuitry, it has steel inside of it.

Battery life

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The Ember Mug 2 comes with a charging pad that you can plug into an AC outlet. The bottom of the mug has a set of rings that contact the charging pins on the pad, so it’ll charge no matter what orientation it’s put away in.

The battery is expected to last up to 1.5 hours. However, we ended up exceeding that in our testing. We filled the mug (set to 140 degrees) with boiling water, threw in a teabag and enjoyed our drink over a 45-minute period. We then immediately did so again for 45 minutes. By the end of this 1.5-hour tea fest, the mug still had 24% battery remaining.

We believe this result had something to do with the water starting higher than our temperature setting and/or there being less liquid to heat up as we sipped. Regardless, two 45-minute sessions is enough for coffee in the morning and tea in the evening. Then, you can charge it up overnight and do it again tomorrow.

As an experiment, we tried heating up cold milk to 140 degrees to see what would happen. The mug was able to bring our drink up to 112 degrees, at which point the LED turned red and the app advised us to charge up. This happened when the mug had 5% battery remaining (it didn’t seem to be heating our drink at this point).

Bottom line

PHOTO: Benjamin Levin/CNN

You really can’t go wrong with the Ember Mug 2. As soon as you pour in liquid, it immediately gets to work maintaining the heat of your drink. And whether you set a custom temperature via the Ember app, or use it at its 135-degree default, it will serve your tastebuds well. The app itself is easy to use, and the mug is easy to clean, though you can’t put it in the dishwasher.

The Ember Mug 2 is available for $99.95.

Note: The prices above reflect the retailer’s listed price at the time of publication.